Hypoxia-inducible factors (HIFs), heterodimeric transcription factors consisting of ? and ? subunits, are master regulators of responses to reduced O2 availability. Three HIFs (HIF-1, HIF-2, and HIF-3) have been identified. HIF-1 and HIF-2 are two key regulators that activate transcription of over 1000 target genes, whose protein products promote cancer growth, invasion, and metastasis. However, HIF-1 and HIF-2 each controls transcription of unique target genes that regulate different aspects of cancer progression. The molecular mechanism for differential regulation of transactivation by HIF-1 vs HIF-2 is not well understood. Understanding regulatory mechanisms of HIF-1- and HIF-2-mediated transactivation will have implications for understanding and treating human cancer. My long-term goals are to elucidate regulatory mechanisms underlying HIF-1- and HIF-2-mediated transactivation in human cancers, to identify therapeutic targets, to develop effective drugs for treatment of human cancers. I have identified a histone demethylase, jumonji domain containing protein (JMJD) 2C, which selectively binds to HIF-1? and stimulates HIF-1-mediated transactivation in human breast cancer cells. But JMJD2C fails to interact with HIF-2? or to regulate HIF-2 target gene transcription. I also found that JMJD2C is highly amplified in human breast cancers and promotes breast cancer growth and metastasis. In this project, I will test a hypothesis that JMJD2C promotes human breast cancer growth and metastasis by coactivating HIF-1, and I will identify novel JMJD2C inhibitors that may be valuable for human breast cancer therapy. In the mentored K99 phase, I will study molecular mechanisms by which JMJD2C selectively coactivates HIF-1 in human breast cancer cells and identify JMJD2C-controlled HIF-1 target genes on a genome-wide scale. In the independent R00 phase, I will define the mechanisms by which JMJD2C promotes human breast cancer growth and metastasis and identify novel JMJD2C inhibitors. The successful completion of the project will provide innovative insights into the molecular mechanism underlying differential regulation of HIF-1- and HIF-2-mediated transactivation in breast cancer. It will also identify a novel therapeutic target and provide potential tools for breast cancer treatment. To achieve the proposed goals, I have assembled a strong mentoring team consisting of Dr. Gregg L. Semenza (Mentor), an internationally recognized leader in the field of HIF-1 and cancer biology, Dr. Saraswati Sukumar (Co-mentor), a nationally recognized expert in breast cancer, Dr. Shyam Biswal (Collaborator), a nationally recognized expert in genome-wide transcriptional analysis, and Dr. Jun Liu (Collaborator), an internationally recognized expert in drug discovery. To successfully accomplish the proposed research, I will obtain training in mouse orthotopic and tail vein models of human cancers, genome-wide ChIP-seq and mRNA-seq analyses, and high- throughput drug screening, and will acquire advanced knowledge in cancer biology, bioinformatics, and drug development as well as comprehensive training in responsible conduct of research during the award period. Overall, the excellent environment of research training at the Johns Hopkins University School of Medicine and Bloomberg School of Public Health will facilitate the successful completion of the proposed research, solidify and expand my expertise, and assure me to make a successful transition to an independent investigator.